Peroral endoscopic myotomy (POEM)

INTRODUCTION — Achalasia results from progressive degeneration of ganglion cells in the myenteric plexus in the esophageal wall. It is characterized by the failure of relaxation of the lower esophageal sphincter (LES), often accompanied by a loss of peristalsis in the distal esophagus. Treatment of achalasia is aimed at decreasing the resting pressure in the LES to allow passage of ingested material.

Achalasia can be treated with pneumatic dilatation, botulinum toxin injection, or surgical myotomy. Laparoscopic Heller myotomy is the most commonly performed surgical myotomy procedure. (See "Surgical myotomy for achalasia".)

Peroral endoscopic myotomy (POEM) is the endoscopic equivalent of surgical myotomy and a newer technique for the management of achalasia. POEM utilizes the principles of submucosal endoscopy to transform the submucosal layer in the esophagus and proximal stomach into a tunnel through which esophageal and gastric myotomy are carried out using a flexible endoscope [1]. Because POEM is performed perorally without any incisions in the chest or abdomen, it is a form of natural orifice transluminal endoscopic surgery (NOTES).

The indications, contraindications, techniques, and outcomes of POEM are discussed in this topic. The clinical manifestations, diagnosis, and other treatment options of achalasia are reviewed elsewhere. (See "Achalasia: Pathogenesis, clinical manifestations, and diagnosis" and "Overview of the treatment of achalasia" and "Surgical myotomy for achalasia".)

PATIENT SELECTION

Indications — POEM can be performed in most patients who have symptomatic, manometrically proven primary idiopathic achalasia. POEM has been endorsed as a primary treatment for type I and II achalasia (as an alternative to pneumatic dilation and surgical myotomy) and a preferred treatment for type III achalasia by major society guidelines [2,3]. The diagnostic evaluation of achalasia is discussed separately. (See "Achalasia: Pathogenesis, clinical manifestations, and diagnosis".)

Although POEM was developed for achalasia, it is increasingly being used to treat other spastic foregut disorders, such as diffuse esophageal spasm (DES) or Jackhammer esophagus [4-9] (see 'POEM for spastic esophageal disorders' below). A detailed discussion of spastic foregut disorders can be found in a separate topic. (See "Distal esophageal spasm and hypercontractile esophagus".)

Additionally, the POEM procedure has been adapted to be performed in the stomach (termed gastric or G-POEM) for the treatment of severe gastroparesis that is refractory to medical therapy in selected patients [10,11]. (See 'POEM for gastroparesis' below and "Treatment of gastroparesis".)

Contraindications — Patients with one of the following conditions should not undergo POEM:

●Severe erosive esophagitis

●Significant coagulation disorders

●Liver cirrhosis with portal hypertension

●Prior therapy that may compromise the integrity of the esophageal mucosa or lead to submucosal fibrosis (eg, radiation, endoscopic mucosal resection, or radiofrequency ablation)

Previous therapies for achalasia, such as pneumatic balloon dilation, botulinum toxin injection, or surgical myotomy, are not contraindications to POEM, although in such cases inflammatory fibrosis may be encountered during submucosal dissection. (See 'Step 2: Creation of submucosal tunnel' below.)

POEM has been successfully performed in patients at both extremes of age. Several series have reported the successful use of POEM in children [12-14].

PREOPERATIVE EVALUATION — Prior to performing a POEM procedure, it is crucial to confirm that patients have the correct diagnosis of achalasia or a spastic esophageal disorder based on the following information:

●Clinical history and physical examination – A standardized, validated symptom assessment form should be completed by all patients, with the majority of centers using the Eckardt score (calculator 1) [15].

●Esophageal manometry – Achalasia or spastic esophageal disorders are subclassified according to the Chicago classification of esophageal motility disorders, which is based upon the result of a high-resolution esophageal manometry test. The clinical significance of this classification, however, has been debated. (See "High resolution manometry", section on 'Classification of motility disorders by esophageal pressure topography (EPT)'.)

●Contrast esophagram – Findings on contrast esophagram that are suggestive of achalasia include a narrowed esophagogastric junction with a "bird-beak" appearance and esophageal aperistalsis. In patients with late- or end-stage achalasia, the esophagus may appear significantly dilated (ie, megaesophagus), angulated, and tortuous, giving it a sigmoid shape. Compared to traditional barium esophagram, the timed barium esophagram (also referred to as timed barium swallow) offers an objective evaluation of the esophageal motility disorders and better prediction of the outcome of therapy [3,16].

●Esophagogastroduodenoscopy (EGD) – EGD may reveal a dilated esophagus that contains residual material, sometimes in large quantities. The esophageal mucosa usually appears normal or with nonspecific changes due to food retention.

●pH study (optional) – We do not routinely perform pH studies if high-resolution esophageal manometry test is diagnostic of a specific spastic disorder. If history or EGD findings suggest gastroesophageal reflux disease, pH study can be performed; however, it is not required.

The diagnostic evaluation of achalasia is discussed in detail elsewhere. (See "Achalasia: Pathogenesis, clinical manifestations, and diagnosis", section on 'Diagnostic evaluation'.)

OPERATIVE MANAGEMENT

Preoperative preparation — All patients are placed on a liquid diet for one to two days prior to a POEM procedure to ensure a clear endoscopic view and avoid aspiration during induction of anesthesia.

Anticoagulant or antiplatelet medications, with the exception of acetylsalicylic acid prescribed for cardiovascular diseases, should be stopped prior to the procedure. Broad-spectrum intravenous antibiotics, such as a second-generation cephalosporin, are administered prior to the procedure.

We prefer to use a high-definition therapeutic gastroscope with both a large suction channel and a dedicated water jet channel for removing food residue in the esophageal lumen [17]. A transparent cap is secured onto the tip of the gastroscope with tape to prevent accidental dislodgement within the submucosal tunnel. Carbon dioxide (CO₂), which is more readily absorbed than air, should be used for insufflation to reduce the risk of mediastinal emphysema, tension pneumoperitoneum, or pneumothorax.

POEM can be performed in the operating room or the endoscopy suite. We perform POEM in the endoscopy suite. The patient is placed supine with the abdomen exposed. A thorough cleansing of the esophageal lumen is performed with water or an antibiotic solution prior to any mucosal incision. Any adherent residue present on the esophageal mucosa can be removed using the cap or suction.

Operative technique — The POEM procedure is carried out in four consecutive steps: 1) mucosal incision and entry into the submucosa, 2) creation of a submucosal tunnel, 3) myotomy, and 4) closure of the mucosal incision (figure 1) [18].

Step 1: Mucosal incision — A mucosal incision is made to allow the gastroscope to enter the submucosal space to create the submucosal tunnel.

The location of the mucosal incision is determined by the level of the esophagogastric junction (EGJ) and the length of the submucosal tunnel required. The length of the submucosal tunnel required is further determined by the length of the myotomy required. In patients with achalasia subtype I or II, a 6 to 8 cm esophageal myotomy is performed. In patients with spastic esophageal disorders, the length of myotomy is typically longer and determined by the proximal extent of the hypertensive contractions as measured by high-resolution esophageal manometry and/or the level of visible spastic contractions seen endoscopically. (See "Achalasia: Pathogenesis, clinical manifestations, and diagnosis", section on 'High-resolution manometry'.)

In most centers, the mucosal incision, submucosal tunnel, and myotomy are created at an anterior position (2 o'clock) of the esophageal lumen. In other centers, a posterior position (5 o'clock) is favored. Randomized trials comparing the two positions found no difference in efficacy or adverse events with up to two-year follow-up [19,20]. A systematic review and meta-analysis found the anterior and posterior myotomy in POEM to be comparable in clinical success, gastroesophageal reflux disease, and adverse event rates, but posterior myotomy required less procedure time (62 versus 82 minutes) [21]. The anterior and posterior positions of the esophageal lumen can be distinguished by injecting water, which pools posteriorly with the patient supine.

Using a mixture of 0.01% epinephrine and 0.25% indigo carmine in 0.9% saline, a submucosal bleb is first raised at a level that is 2 to 3 cm above the proximal margin of the intended myotomy. Either a triangular tip knife or a HybridKnife can be used to make a 1.5 to 2 cm longitudinal mucosal incision using dry cut mode at 50 watts on effect 3 (ERBE). HybridKnife has the advantage of permitting both needleless, high-pressure water jet injection and electrosurgical dissection without accessory exchange. The gastroscope is then maneuvered into the submucosal space after dissecting the submucosal fibers at the mucosal incision with the knife.

Step 2: Creation of submucosal tunnel — A submucosal tunnel is created toward the stomach using a technique similar to endoscopic submucosal dissection. Using the knife, the submucosa is dissected with a no-touch technique using spray coagulation mode at 50 watts on effect 2 (ERBE) in a plane that is located nearly on the surface of the muscularis propria. Whenever the dissection plane becomes unclear, repeated jet injection of the same mixture of epinephrine, indigo carmine, and saline is performed to enhance the demarcation between the submucosal layer and the muscularis propria.

The gastroscope must be properly oriented as it is advanced through the submucosal tunnel to preserve the integrity of the mucosal layer. After myotomy, the mucosal layer becomes the only remaining barrier between the mediastinum/peritoneum and the esophageal/gastric lumen.

Larger blood vessels in the submucosa are coagulated using hemostatic forceps (eg, Coagrasper in soft coagulation mode at 80 watts on effect 5, ERBE) or the HybridKnife.

The submucosal tunnel is extended until it is 2 to 3 cm beyond the EGJ, passing where the "clasp and sling" fibers maintain the continence of the lower esophageal sphincter (LES) (figure 2). Complete division of these "clasp and sling" fibers is essential to the success of myotomy.

The EGJ can be located endoscopically by multiple methods, including insertion depth, narrowing of the submucosal space and resistance of passage of the endoscope through the EGJ followed by prompt expansion of the space at the gastric cardia, change in vasculature, visualization of aberrant longitudinal muscle fibers at the EGJ, or injection of epinephrine or indocyanine green (ICG) [22,23]. When the gastroscope is positioned in the lumen of the stomach, extension of the submucosal tunnel past the EGJ can also be confirmed by retroflexing and visualizing adequate levels of color change caused by indigo carmine in the submucosa.

Step 3: Myotomy — Selective myotomy of the inner circular muscle bundles is performed starting 2 cm distal to the mucosal incision. Circular muscle bundles are individually lifted toward the submucosal tunnel by the sharp tip of the knife and divided with spray coagulation current at 50 watts on effect 2 (ERBE).

Selective myotomy of the inner circular muscle proximal to the LES with preservation of the outer longitudinal esophageal muscular layer is often performed during POEM to avoid entering the pleural space. When performed by less experienced operators, such technique adds a "safety net" to the procedure.

However, selective myotomy is often hard to achieve because the longitudinal muscle fibers of the esophagus are extremely thin and prone to splitting during dissection. Furthermore, the plane that separates the circular and longitudinal muscular layers becomes difficult to delineate beyond the esophagus.

The optimal depth of myotomy is not known; the advantages of selective inner circular muscle versus full-thickness myotomy are only theoretical. One retrospective study suggested that both techniques were equally effective and safe, although full-thickness myotomy was associated with a shorter procedure time [24].

In terms of length of myotomy, it is essential to achieve a 2 to 3 cm myotomy into the gastric cardia. It is customary to perform a 6 cm myotomy on the esophageal side in patients with achalasia type I and II. In a trial of treatment-naïve patients with type II achalasia, a "short" myotomy performed equally as a standard (10 cm) myotomy while reducing procedural time and the risk of abnormal esophageal acid exposure at one-year follow-up [25].

In patients with spastic esophageal disorders, a longer esophageal myotomy is typically needed and should be dictated by manometric and endoscopic findings. In principle, the spastic esophageal segment should be included in the myotomy.

Step 4: Closure of mucosal incision — Before closure of the mucosal incision, a careful inspection of the submucosal tunnel is performed and any bleeding is controlled. The esophageal mucosa is then inspected, and any incidental tear (ie, mucosotomy) is closed. Adequate LES relaxation is confirmed by a retroflexed view of the gastric cardia.

Closure of the mucosal incision can be performed with endoscopic clips [23,26] or with an endoluminal suturing device (eg, OverStitch) [27]. When endoscopic clips are used, the initial clip is placed at the most distal part of the incision to facilitate approximation of the incision borders. Subsequent clips are then placed in a distal to proximal direction until the mucosal incision is completely closed.

POSTOPERATIVE CARE — Patient care after POEM procedures has not been standardized. Patients are typically admitted to the hospital for overnight observation and kept nil per os and given antibiotics and antiemetics prophylactically. Some experts obtain a water-soluble contrast esophagram on the day after the procedure to exclude an esophageal leak [28], after which a soft diet is allowed. Patients are advised to remain on a soft diet for 7 to 10 days before starting a regular diet. However, due to its established safety, it is now feasible to perform POEM as an outpatient procedure [29,30].

●In our practice, patients who undergo an uneventful procedure with secure mucosal closure (high confidence) are discharged home after a two-hour observation in the endoscopy unit. Patients are allowed to drink clear liquids at that time and start a soft diet the next day.

●A small randomized trial found that routine antibiotics beyond the prophylactic dose may not be necessary because of a very low residual infective risk [31]. In our practice, patients are routinely prescribed antibiotics for approximately three days.

●We also prescribe daily proton pump inhibitors (PPIs). The decision on continuing or stopping PPIs during follow-up should depend on reflux symptoms, findings during repeat endoscopy (if performed), and/or results of pH studies.

●During subsequent clinic visits, patients are assessed for any delayed complications and clinical response to POEM (eg, by Eckardt score) (calculator 1).

OUTCOMES OF POEM FOR ACHALASIA

POEM for primary achalasia

Efficacy and durability — POEM is highly efficacious in the short-term management of achalasia. According to a 2014 summary of 14 studies of POEM, clinical success, defined as a post-treatment Eckardt score of ≤3 and/or a >50 percent decrease in the lower esophageal sphincter (LES) pressure, was achieved in 82 to 100 percent of patients [32]. Other studies documented similar patient improvements after POEM using either timed barium esophagram [27,33,34] or quality of life assessment [27,35].

The durable clinical success rate of POEM (usually defined as an Eckardt score of ≤3) was between 78 and 92 percent at between two and seven years [36-41]. Less than 4 percent of patients required retreatment for achalasia [38,40]. Patient with nonspastic (type I or II) achalasia did better than patients with spastic (type III) achalasia or other spastic esophageal disorders [37,39,40]. (See 'POEM for spastic esophageal disorders' below.)

In a multicenter retrospective study involving 117 pediatric patients undergoing POEM for achalasia, clinical success was achieved in 91 (95% CI 84-95) percent of cases after a mean follow-up of 545 days [42]. There were a total of seven adverse events, and 15 percent of patients had gastroesophageal reflux symptoms. There was also a trend toward more frequent clinical failure in achalasia associated with genetic disorders (40 versus 8 percent).

Comparison with surgical myotomy — The efficacy and safety of POEM has been compared with that of laparoscopic Heller myotomy (LHM) [43]. In a randomized trial of 221 patients with idiopathic achalasia, POEM and LHM with Dor fundoplication were equally successful in controlling symptoms (Eckardt symptom score ≤3) at two years (83 versus 82 percent). Compared with LHM, POEM was associated with a lower rate of severe adverse events (2.7 versus 7.3 percent) but a higher rate of reflux esophagitis (57 versus 20 percent at three months; 44 versus 29 percent at two years) [44].

In a meta-analysis of over 7000 patients in over 70 cohort studies, POEM was more effective than LHM in relieving dysphagia [45]. Predicted probabilities for improvement in dysphagia at 12 months were 93.5 percent for POEM and 91.0 percent for LHM and at 24 months were 92.7 percent for POEM and 90.0 percent for LHM; both differences were statistically significant. However, POEM was associated with higher incidences of pathologic reflux by multiple measurements (symptoms, erosive esophagitis, and abnormal pH studies) and a slightly longer hospital stay (by one day) than LHM. Studies on LHM had significantly longer follow-up than POEM (41.5 versus 16.2 months); longer-term data on POEM are required before the durability of the two procedures can be directly compared.

Based on current literature, patients with achalasia should be informed that POEM and LHM are equally effective in relieving swallowing difficulties but POEM results in more reflux and LHM has more adverse events. Thus, the choice may depend on available local resources and patient/surgeon preference. (See "Surgical myotomy for achalasia", section on 'Fundoplication'.)

Comparison with pneumatic dilation — In a trial of 133 treatment-naïve patients with achalasia, POEM resulted in a higher rate of treatment success than pneumatic dilation at two years (92 versus 54 percent, p<0.001) [46]. No procedure-related adverse events occurred after POEM, while one perforation occurred with pneumatic dilation; reflux esophagitis developed more frequently after POEM than after pneumatic dilation (41 versus 7 percent, p = 0.002). If these results are validated, POEM could replace pneumatic dilation as the primary endoscopic therapy for achalasia, while pneumatic dilation in the future may play a role in treating recurrent dysphagia after LHM or POEM. (See "Overview of the treatment of achalasia", section on 'Choice of treatment'.)

In a retrospective cohort study of commercially insured patients who underwent either LHM, pneumatic dilation (PD), or POEM for achalasia in the United States between July 1, 2010, and December 31, 2017, the use of POEM increased from 1.1 percent (95% CI 0.2-3.2) of procedures in 2010 to 18.9 percent in 2017 (95% CI 13.6-25.3) [47]. Compared with LHM, POEM was associated with more subsequent diagnostic testing (incidence rate ratio [IRR] 2.2, 95% CI 1.9-2.6) and reinterventions (IRR 1.9, 95% CI 1.1-3.3). When compared with PD, POEM was associated with more subsequent diagnostic testing (IRR 1.5, 95% CI 1.3-1.8) but fewer reinterventions (IRR 0.4, 95% CI 0.2-0.6). The total one-year health care costs were similar between POEM and LHM, but significantly lower for PD (mean cost difference $7674; 95% CI $657-$14,692).

POEM for recurrent achalasia — POEM has been shown to be feasible, safe, and effective in treating patients who have failed other prior endoscopic or surgical treatment for achalasia [48-50].

According to the International Per Oral Endoscopic Myotomy Survey (IPOEMS), 40 percent of POEM procedures were performed in patients with prior endoscopic therapy for achalasia [22]. Although submucosal fibrosis caused by prior botulinum toxin injection or pneumatic dilation may render the dissection more challenging, the general consensus among the POEM operators was that the efficacy was not compromised in such patients [22].

Recurrent or persistent symptoms can occur in approximately 10 to 20 percent of patients who undergo LHM [51]. When performed by experienced operators, POEM is a viable rescue option for patients who develop recurrent or persistent symptoms after a Heller myotomy.

●In a 2021 systematic review and meta-analysis of nine retrospective studies including 272 patients who had prior Heller myotomy, POEM was technically successful in over 99 percent and clinically successful in 90 percent [52]. Most adverse events were self-limited or conservatively managed.

●One randomized trial compared POEM with PD in patients with persistent or recurrent symptoms after LHM [53]. A total of 90 patients were included. POEM had a higher success rate (28 of 45 patients [62.2 percent]) than PD (12 of 45 patients [26.7 percent], p = 0.001). Reflux esophagitis was not significantly different between POEM and PD (34.3 versus 15 percent).

POEM procedures can be repeated in patients who develop recurrent symptoms after a previous POEM procedure, typically on the opposite side of the esophagus. In a multicenter retrospective study of 46 patients with failed POEM, redo POEM was technically and clinically successful in 100 and 85 percent, respectively. The average Eckardt score decreased from 4.3±2.48 to 1.64±1.67 after redo POEM [54].

Adverse events — When performed by experienced operators, POEM is a safe procedure that is associated with a low rate of postoperative adverse events [55]. Most complications that occur after POEM can be managed expectantly, medically, or endoscopically.

In an international multicenter study that included 1826 patients who underwent POEM, 137 patients experienced one or more adverse events (prevalence of 7.5 percent) [56]. The 156 adverse events varied in severity (116 mild, 31 moderate, and 9 severe). A total of 51 inadvertent mucosotomies occurred in 2.8 percent of patients.

Pneumoperitoneum — Small pneumoperitoneum and subcutaneous emphysema are experienced during 50 and 15 percent of POEM procedures, respectively [32]. They typically resolve spontaneously. Severe or tension pneumoperitoneum is rare but requires prompt detection and decompression when it occurs.

The abdomen is palpated periodically throughout the procedure to exclude severe pneumoperitoneum. If the abdomen becomes excessively distended, especially if the tidal volume begins to diminish or the peak and plateau airway pressures begin to rise, abdominal decompression is performed using a Veress needle or an angiocatheter. Prior to decompressing the abdomen, the operator must be sure that the abdominal distention and/or respiratory compromise are secondary to excessive abdominal (peritoneal) insufflation, rather than gastric insufflation, by first desufflating the stomach endoscopically.

Pneumothorax — Pneumothorax is infrequently encountered (<5 percent of cases) but does not usually require treatment, as carbon dioxide used for insufflation is rapidly absorbed. Chest tube insertion is only required in case of respiratory compromise to allow the procedure to be continued.

Mucosal tear — Inadvertent mucosal tears (mucosotomy) during POEM require prompt closure because they represent full-thickness esophageal perforations after all other layers of the esophageal wall have been divided. Most mucosotomies occur at the level of the LES and cardia where the submucosal tunnel narrows. Small mucosotomies can be closed with endoclips; larger mucosotomies have to be closed with an endoluminal suturing device (eg, OverStitch) [57,58]. Alternatively, mucosotomies can also be closed with fibrin glue [59] or over-the-scope clips [60]. When a mucosotomy is detected during submucosal tunneling, it should be closed immediately, or else its size may increase rapidly.

Mediastinitis from esophageal leak is the most feared complication of POEM but is remarkably rare (<0.1 percent of cases) [32].

Bleeding — Bleeding during submucosal tunneling is not uncommon. The risk of bleeding can be minimized with a careful stepwise dissection to allow for visualization of individual blood vessels. Small vessels can be prophylactically coagulated with the electrocautery knife itself; hemostatic forceps (eg, Coagrasper) should be used to coagulate larger vessels in the gastric cardia. If bleeding appears to originate from a vessel along the mucosal surface, hemostasis can be achieved with gentle pressure applied with the tip of the gastroscope for several minutes, rather than with electrocautery.

In a large series of 428 patients, delayed bleeding occurred in 0.7 percent of patients [61]. Patients who present with hematemesis after a POEM procedure, with or without chest pain, should undergo emergency endoscopy, during which the clips or sutures used to close the mucosal incision must be removed and the submucosal tunnel and myotomy site inspected for bleeding.

Gastroesophageal reflux — The most common late adverse event associated with POEM is gastroesophageal reflux (GER). Based on objective data (endoscopic-proven erosive esophagitis and/or abnormal pH study), the prevalence of GER after POEM varies between 20 and 57 percent, depending on studies [32].

A 2018 meta-analysis found the prevalence of GER to be higher after POEM than after LHM with fundoplication both in terms of symptoms (19.0 percent POEM versus 8.8 percent LHM), abnormal pH study (39 percent POEM versus 17 percent LHM), and esophagitis (28 percent POEM versus 7.6 percent LHM) [62]. (See 'Comparison with surgical myotomy' above.)

An observational study of 183 patients published after the meta-analysis reported subjective, objective, and severe objective GER in 38.8, 50.5, and 19.2 percent of patients, respectively, at about two years after POEM [63]. The independent predictors for objective GER were normal preoperative diameter of esophagus (odds ratio [OR] 3.4) and LES pressure less than 45 mmHg (OR 1.86). The independent predictors for severe objective GER were LES pressure less than 45 mmHg (OR 6.57) and obesity (OR 5.03). Modifiable factors such as the length of esophageal or gastric myotomy or indication of procedure had no impact on the incidence or severity of GER.

POEM FOR DISEASES OTHER THAN ACHALASIA — Although it was originally developed for achalasia, POEM has been used to treat other upper esophagogastric diseases, such as spastic esophageal disorders and gastroparesis.

POEM for spastic esophageal disorders — Spastic esophageal disorders (SEDs) are characterized by hyperactive esophageal contractions of either abnormal propagation (premature contraction) or extreme vigorous contraction [64]. Examples of SEDs include spastic or type III achalasia, distal esophageal spasm (DES), hypercontractile (jackhammer) esophagus, and hypertensive esophageal peristalsis (nutcracker esophagus). (See "Distal esophageal spasm and hypercontractile esophagus".)

POEM has been used to treat jackhammer esophagus, DES, spastic achalasia, and nutcracker esophagus [4-9,27,65-67]. A meta-analysis of nine studies reported a pooled success rate of 90 percent (95% CI 84-93 percent) [68]. Neither total myotomy length nor prior treatment status had an impact on the clinical success rate.

Myotomy of the esophageal body (where hypertensive contractions occur), in addition to the lower esophageal sphincter (LES), may be required to treat SEDs [5,64]. Surgical myotomy of the upper thoracic esophagus via the transabdominal approach is technically challenging [69]. By contrast, POEM allows access to the entire esophagus, which makes it a potentially more effective treatment for SEDs than surgical myotomy [4,5,7-9]. As an example, in a retrospective study of spastic (type III) achalasia, 49 patients who underwent POEM had a higher clinical response rate than 26 patients who underwent laparoscopic Heller myotomy (98 versus 81 percent) [65]. POEM was also associated with a shorter operative time (102 versus 264 minutes), a longer myotomy (16 cm versus 8 cm), and fewer adverse events (6 versus 27 percent).

POEM for gastroparesis — Gastroparesis is a syndrome of delayed gastric emptying in the absence of a mechanical obstruction, which usually presents with symptoms of nausea, vomiting, early satiety, bloating, or upper abdominal pain. Most cases of gastroparesis are idiopathic, diabetic, or postsurgical. (See "Gastroparesis: Etiology, clinical manifestations, and diagnosis".)

Initial management of gastroparesis consists of dietary modification, optimization of glycemic control and hydration, and pharmacologic therapy with prokinetic and antiemetic medications. Patients who are refractory to medical therapy may require surgical interventions in the forms of tube gastrostomy, subtotal gastrectomy, or pyloroplasty. (See "Treatment of gastroparesis".)

Surgical pyloroplasty (eg, Heineke-Mikulicz pyloroplasty) can lead to sustained improvement of symptoms in patients with refractory gastroparesis [70]. Gastric peroral endoscopic myotomy (G-POEM), which is an endoscopic equivalent of surgical pyloroplasty, has been performed in a few centers for severe refractory diabetic gastroparesis [10].

Technique of G-POEM — The endoscopic pyloromyotomy (G-POEM) procedure myotomizes the pylorus, rather than the lower esophageal sphincter; otherwise, G-POEM consists of the same four steps as described above for POEM (see 'Operative technique' above). For G-POEM, a submucosal tunnel is typically created 5 cm proximal to the pylorus along the greater curvature or anterior gastric wall. A short (2 cm) antral myotomy is then performed in addition to pyloromyotomy via the submucosal tunnel.

Postoperative care for G-POEM is the same as for POEM, except that a gastric emptying study is typically performed during follow-up to assess the effect of the myotomy on gastric emptying. (See 'Postoperative care' above.)

Outcomes of G-POEM for gastroparesis — Multiple case series showed that G-POEM is safe, feasible, and effective in treating severe refractory gastroparesis [71-76].

●In a randomized trial of 41 patients with severe gastroparesis (17 diabetic, 13 postsurgical, 11 idiopathic), clinical success was significantly higher in the G-POEM group than the sham control (diagnostic upper endoscopy, 71 versus 22 percent, p = 0.005) [77]. Median gastric retention at four hours decreased from 22 to 12 percent after G-POEM and did not change after sham. A total of 12 patients crossed over to G-POEM with 9 (75 percent) achieving clinical success.

●In a 2023 systematic review and meta-analysis of four nonrandomized studies comparing G-POEM with surgical pyloromyotomy or pyloroplasty for gastroparesis, The mean procedural time (MD: -59.47 mins, p <0.001) and length of hospital stay (MD: -3.10 days, p <0.001) was significantly lower for G-POEM compared with surgery [78]. The post procedure GCSI score (MD: -0.33, p = 0.39) and reduction in GCSI score preoperatively and postoperatively (MD: 0.27, p = 0.55) was not significantly different.

POEM for Zenker's diverticula — A variety of endoscopic techniques have been described for the treatment of Zenker's diverticula (ZD) with clinical success rates between 56 and 100 percent and adverse events in an average of 15 percent of cases [79]. Clinical recurrence occurs in 10.5 percent of patients, but recurrence rates up to 35 percent have been reported. It is not possible to accurately delineate the terminal end of the diverticulum during standard endoscopic Zenker's septotomy, and recurrence has been linked to incomplete septotomy. (See "Zenker's diverticulum", section on 'Flexible endoscopy'.)

POEM could be a promising technique to allow complete transection of ZD septum (Z-POEM), as submucosal tunneling enables complete exposure and dissection of the septum [79-81]. This may result in diminishing the risk of symptom recurrence.

Techniques of Z-POEM — A mucosal bleb is created 1 to 2 cm proximal to the ZD septum [82]. A 1 cm incision, serving as the tunnel entry, is then created using Endo Cut Q current effect 3 (picture 1). The submucosal fibers are dissected with spray coagulation (40 W, effect 2), and the endoscope then enters the submucosal space with the aid of the clear cap. A submucosal tunnel is created using spray coagulation and injection of indigo carmine solution until the thick diverticular septum is identified. The tunnel is continued on both the diverticular side and esophageal side until the bottom of the diverticulum is reached and the septum is entirely exposed. Septotomy can then be accomplished using ESD knives (eg, stag beetle knife) and Endo Cut Q current at 50 W and effect 3. Under direct endoscopic view, the muscle fibers of the septum are completely dissected down to the bottom of the diverticulum. Subsequently, a 1 cm distal extension of the myotomy on the esophageal side is performed to ensure complete septal dissection. Finally, the mucosal incision is closed with standard clips.

Outcomes of Z-POEM for dysphagia

●One study included 75 patients (73.3±1.2 years, female n = 33) with a mean size of ZD of 31.3±1.6 mm (10 to 89 mm) [79]. The overall technical success rate was 97.3 percent (73/75). There were technical failures due to inability to locate the septum and failed tunnel creation. Adverse events occurred in 6.7 percent (5/75) of cases: one bleed (mild) conservatively managed and four perforations (one severe, three moderate). The mean procedure time was 52.4±2.9 minutes, and the mean length of hospital stay was 1.8±0.2 days. Clinical success was achieved in 92 percent (69/75) of patients with a decrease in mean dysphagia score from 1.96 to 0.25. At one-year follow-up, one patient reported symptom recurrence.

●Another study that included 89 patients with ZD assessed the long-term outcomes of Z-POEM [83]. The mean diverticulum size was 3.4 ±1.3 cm. Technical success was achieved in 97.8 percent of patients (n = 87) with a mean procedure time of 43.8 ±19.2 minutes. The median postprocedure hospital stay was one day. There were eight adverse events (9 percent; three mild, five moderate). Overall, clinical success was achieved in 84 patients (94 percent). Symptom recurrence occurred in six (6.7 percent) patients during a mean length of follow-up of 37 months (range 24 to 63 months).

POEM for other esophageal diverticula — POEM can also be utilized for the management of esophageal diverticula other than ZD (D-POEM). Conceptually, any esophageal diverticulum with a significant septum can be treated with POEM.

●One small study included 11 patients with an esophageal diverticulum (Zenker's 7, mid-esophagus 1, epiphrenic 3) [82]. The mean size of the esophageal diverticula was 34.5 mm. Technical success was achieved in 10 patients (90.9 percent) with a mean procedure time of 63.2 minutes. There were no adverse events. Clinical success was achieved in all 10 cases with a decrease in mean dysphagia score from 2.7 to 0.1 during a median follow-up of 145 days (interquartile range 126 to 273).

●Another study included 25 patients (Zenker’s 20, epiphrenic 5) [84]. POEM was technically successful in all patients. At 12 months, clinical success was achieved in 86 percent of patients without any long-term adverse events.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Achalasia".)

SUMMARY AND RECOMMENDATIONS

●Definition – Peroral endoscopic myotomy (POEM) is a form of natural orifice transluminal endoscopic surgery (NOTES) that utilizes the principles of submucosal endoscopy to perform the endoscopic equivalent of a surgical myotomy. (See 'Introduction' above.)

●Indications – POEM can be performed in most patients who have symptomatic, manometrically proven primary idiopathic achalasia. Previous therapies for achalasia, such as pneumatic balloon dilation, botulinum toxin injection, or surgical myotomy, are not contraindications to POEM. (See 'Indications' above.)

●Contraindications – Patients who have severe erosive esophagitis, significant coagulation disorders, liver cirrhosis with portal hypertension, or prior therapy that may compromise the integrity of the esophageal mucosa or lead to submucosal fibrosis (eg, radiation, endoscopic mucosal resection, radiofrequency ablation) should not undergo POEM. (See 'Contraindications' above.)

●Operative techniques – POEM is typically performed in four consecutive steps: mucosal incision, creation of a submucosal tunnel, myotomy, and closure of mucosal incision (figure 1). (See 'Operative technique' above.)

●Outcomes – The short-term success rate of POEM for achalasia, 82 to 100 percent, is comparable to that of laparoscopic Heller myotomy and superior to that of pneumatic dilation. Longer-term studies revealed success rates of 78 to 92 percent at two to seven years. POEM also appears to be a viable treatment option for patients who develop recurrent or persistent symptoms after other treatments of achalasia, such as pneumatic dilatation, botulinum toxin injection, or surgical myotomy. (See 'Outcomes of POEM for achalasia' above.)

●Adverse events – Adverse events associated with POEM include pneumoperitoneum, subcutaneous emphysema, pneumothorax, mucosotomy, bleeding, and gastroesophageal reflux. The incidence of adverse events is low (about 8 percent), and most of the adverse events can be managed expectantly, medically, or endoscopically. (See 'Adverse events' above.)

●Other POEM techniques – The POEM technique has been successfully used to treat spastic esophageal disorders (eg, spastic achalasia, distal esophageal spasm, jackhammer esophagus, or nutcracker esophagus), severe gastroparesis refractory to medical therapy (G-POEM), and Zenker's diverticula (Z-POEM). (See 'POEM for diseases other than achalasia' above.)